Factor xiii

F-XIII is an alpha-2-globulin tetramer of two-alpha and two beta chains with a molecular weight of 320,000 D. Its half-life is 8 days. The alpha chains are formed in megakaryocytes and macrophages, while the beta chains are synthesized in the liver. F-XIII is detectable in platelets, monocytes and tissue.
The enzymatic activity lies in the alpha chains. It is a transglutaminase which, when activated, crosslinks the fibrinomers and produces the isopeptide bond. This converts the soluble fibrin polymer into the soluble fibrin polymer.

The factor XIII is activated by thrombin and calcium ions. This produces the active transglutaminase, which cross-links the alpha and beta chains of the fibrin. In addition to the fibrin-stabilizing effect, factor XIIIa also intervenes in the process of tissue repair and wound healing. F-XIII deficiency therefore leads not only to increased bleeding but also to wound healing disorders. Furthermore, factor XIII is also involved in the processes of cell adhesion, cell migration and the formation of the extracellular matrix.

Further functions of F-XIII are the binding to alpha-2-antiplasmin, to fibroectin and to collagen. F-XIII stabilizes the endothelial barrier by protein cross-linking during reperfusion processes and strengthens the protective function of the endothelium. In liver diseases the concentration of F-XIII may be reduced.

The factor XIII was described by Robins in 1944. Laki and Lorand published a paper on it in Science in 1948.

1. HA Neumann (2014) The coagulation system. ABW-Wissenschaftsverlag GmbH Berlin S. 67f.